The present invention relates to a centrifuge with a self-emptying drum, wherein the wall of the drum has expulsion apertures that lead from a solids space and that can be closed off by a piston slide, wherein a closure chamber, which has channels that closure liquid is supplied through, is associated with the piston slide, wherein the circumference of the closure chamber has at least one outlet channel with the associated hydraulically regulated body of a valve, and wherein the outlet channel opens into a chamber that bleed perforations, each of which has a constriction, extend out of through the wall of the drum.
A centrifuge of this type is known, from German Pat. No. 3,208,808 for example. The bleed channel is a perforation that has a sealing plate secured to a cam-like projection associated with it. There are usually several bleed channels of this type distributed uniformly around the circumference to maximize the flow cross-section. Still, the number and diameter of the bleed channels and hence the overall cross-section available for bleeding the closure water out of the closure chamber is limited by economics and structural strength. Also, a valve body with radial projections is relatively expensive to manufacture, and the sealing plate has close tolerances because an unobjectionable seal can only be attained when there are several sealing plates when their surfaces are precisely in one plane. How fast the closure liquid can be bled out of the closure chamber depends or, among other factors, the flow cross-section of the bleed channels. The more rapidly the liquid is bled out, the longer the attainable opening stroke of the piston slide to extract a prescribed portion of the contents of the drum. The opening stroke must be long to ensure extraction of solids that tend to bridge subject to powerful centrifugal forces within the drum. Thus, the attainable piston-slide stroke is a compromise.